1. Field of the Invention
The present invention relates generally to the field of power tools. In particular the present invention relates to a tool-free collet assembly for gripping interchangeable tool accessories, such as drill bits, and including a dust management system.
2. Discussion
Various types of tools require a user to selectively attach a tool accessory such as a drill or router bit. Over the course of a particular project or work period it may be necessary to employ a variety of such accessories and to replace worn or broken ones. Convenient removal and replacement of the interchangeable tool accessories is therefore desirable. Two commonly employed mechanisms for holding interchangeable accessories are chucks and collets. Collet type mechanisms are usually favored for tools with higher rotational speeds.
In a collet-type holder the shank of a tool accessory is inserted into the bore of a collet. A collet is a generally cylindrical element with a longitudinal bore. The collet has at least one end with a plurality of longitudinally extending arcuate jaws arranged equiangularly around the circumference of the collet and spaced apart by a plurality of longitudinally extending cuts. The collet may be machined into the end of a tool output element (such as a shaft, spindle or arbor) or it may be a separate (sometimes barrel-shaped) element.
Over the collet is installed a collet nut or collet ring. The collet nut is threaded onto the end of the tool shaft or spindle. Threading the collet nut down on the spindle causes surfaces on the inside of the collet nut and/or shaft to compress the jaws of the collet around the shank of the tool accessory. Thus, the tool accessory is secured to the power tool shaft/spindle.
When changing accessory tools, the nut must be loosened to allow the collet to expand and release its grip on the tool accessory. The tightening and loosening of the collet nut may be partially performed by hand, but the size and shape of the collet nut make it difficult and/or uncomfortable to properly tighten and then initially loosen the collet nut using hands alone. Therefore, it is necessary to use a hand wrench or similar tool in order to apply sufficient torque to the collet nut.
In the case of rotary or power tools, when tightening or loosening the collet nut, the shaft/spindle must be prevented from rotating or else it would be difficult to achieve relative motion between the nut and the rotatable spindle.
Conventionally, the loosening and tightening process requires that the operator simultaneously grip both the shaft/spindle and the collet nut with two separate hand wrenches or the like. Then a torque is applied to the nut while the shaft is held in place. This is an awkward process and made even more so by the necessity to support the weight of the tool itself.
More recently, tools have been designed that incorporate a locking mechanism that locks the shaft/spindle relative to the tool housing. Thus, the rotation of the shaft can be prevented, simply by employing the built in shaft lock. For such a power tool, only one hand wrench is required to loosen or tighten the collet nut. See, for example, U.S. Pat. Nos. 5,496,139 and 5,813,805.
The need to use even one hand tool to change tool accessories, however, is still inconvenient. For example, when a bit replacement is required, the tool operator has to stop what he is doing to find a wrench. This delay can be meaningful in jobs, such as drywall installation during major construction or remodeling projects, where high production rates are essential.
Because many of the tools that may incorporate this invention are employed in dust and debris producing tasks, it is desirable that any features added to such tools be designed to resist fouling by dust.
It is, therefore, one object of the invention to provide a tool with a collet assembly that allows the user to conveniently install or remove an accessory without the use of any hand tools.
It is another object of the invention to provide an operating member with an exposed and graspable collet grip that provides enough mechanical advantage to permit the operator to exert sufficient torque for tightening or loosening the collet nut without having to use a hand tool.
This and other objects of the invention are attained by a tool-free collet assembly with an integral collet wrench. The collet wrench is rotatably mounted on the tool for turning the collet nut so as to tighten or loosen the collet. The collet wrench is also movable between an engaged position, wherein the collet wrench can turn the collet nut, and a disengaged position, wherein the collet wrench does not restrain the collet nut and does not interfere with normal rotation of the collet nut when the tool is operated. The movement of the collet wrench between the engaged and disengaged positions could be axial, radial, rotational, or some combination thereof.
The collet wrench may be biased into the disengaged position. This may be accomplished by a spring or other means for exerting a biasing force.
An operating member may connect the collet wrench to the tool. The operating member supports the collet wrench for movement between the engaged and disengaged position. The operating member may also be moveably mounted on the tool for imparting movement to the collet wrench. The operating member may include an externally exposed and manually graspable collet grip. By means of the collet grip, the operator can move the collet wrench rotationally and/or axially.
A collet wrench button may also be provided for moving the collet wrench between the engaged and disengaged position.
The collet wrench itself may be of several types. It may be of an open end or closed end (box wrench) type design. Alternatively, it may be of a complex interior shape. Such a complex shape may have two portions. A first portion corresponds to the disengaged position and within that first portion the collet nut may freely rotate during normal operation of the tool. The second portion corresponds to the engaged position and the surface of the second portion is shaped to contact and turn the collet nut.
The collet nut and/or the spindle on which it is threaded may be partially coated with a non-stick material to reduce the torque necessary to loosen the collet. The nonstick material could be, for example, Teflon(copyright).
The internal surfaces of the collet nut and the spindle may cooperate with interchangeable collets having substantially identical external geometries and dimensions, but having different bores for gripping accessories with shanks of various diameters and geometries.
Another feature of this invention is an improved spindle lock design. The improved design is similar to that of the collet wrench and may incorporate either an open-ended wrench or one of complex shape as described within.
Certain jobs employing rotary cutout and router tools, for example drywall cutting, produce dust that can get inside the tool and foul the operation of the buttons and operating member. Therefore, it is still another object of the invention to provide a tool free collet assembly that is resistant to fouling in a dusty or dirty environment. This object is accomplished by a design that accepts that the entrance of some dust is inevitable and works to ensure that dust that gets into the mechanisms can also get out and does not accumulate to levels that interfere with the operation of the tool. This design incorporates several basic features or techniques, which coact to produce a dust management system as follows:
the use of looser tolerance between parts that move relative to each other;
the avoidance or minimization of interior dead ends or pockets from which dust can escape only very slowly;
the action of moving parts incidentally tends to move or push dust along a general flow path towards intended exit points;
horizontal or vertical boundaries between sub assemblies are provided with through holes to permit the movement of dust; and
interior components do not fit closely against the exterior sheath or housing around the entire interior perimeter so that dust is able to move around those components.
This dust management design approach is principally a passive one. That is, it does not provide a dedicated means for forcing the dust out. Rather, it seeks to avoid trapping the dust and relies on a dust flow arising from the movement of the tool as the operator uses it and randomly moves it about in various positions and orientations. Some impetus may be given to the dust by motion of moving parts and by the cooling air flows produced by a motor fan. Lastly, the same features that discourage dust build up also allow for easier cleaning of the tool, for example by blowing out with compressed air, if that becomes necessary.